Stock material or miscellaneous articles – Composite – Of metal
Patent
1993-03-12
1995-01-31
Acquah, Samuel A.
Stock material or miscellaneous articles
Composite
Of metal
528272, 528302, 528308, 428457, 428480, 428482, 525437, 4272071, 427216, 427217, 427218, 427221, 427231, 427233, 427234, 264533, 264544, 264129, B32B 1508, B29C 5300
Patent
active
053857887
DESCRIPTION:
BRIEF SUMMARY
This invention is concerned with improvements in and relating to polyester resins. More particularly, the invention is concerned with saturated, film-forming polyester resins suitable for use in coating compositions, especially coloured or pigmented coating compositions such as decorative or protective inks.
With the introduction of so-called "necked" cans for beverages, there has arisen a need for tough, flexible coating compositions for application to the cans, before necking, which compositions will withstand the deformation caused by the necking process.
It has now been found, in accordance with the present invention, that saturated, film-forming polyester resins derived, inter alia, from certain long chain alcohols (as hereinafter defined) can be useful components of coating compositions for application, for example, to cans which are later to be necked.
According to the invention, therefore, there is provided a film-forming polyester resin which is, inter alia, derived from a monohydric alcohol component comprising one or more long chain alcohols as hereinafter defined, the said alcohol forming from 5 to 60% by weight of the components from which the polyester is derived.
By the term "long chain monohydric alcohol", as used herein, we mean a saturated or unsaturated monohydric alcohol having a hydroxyl group attached to an organic residue comprising a straight or branched chain, which chain may be interrupted by one or more hetero-atoms (such as oxygen, sulphur or nitrogen atoms); the chain structure containing a total of at least six carbon atoms (and hereto-atoms, if any), preferably from 6 to 20, especially 10 to 24 carbon atoms (and hetero-atoms, if any). acids; alcohols; and, optionally, and/or one or more monocarboxylic acids.
The polyesters may, and often will, be prepared by polycondensation of a mixture of the above ingredients. However, they may also be prepared in stages, e.g. by the polycondensation of the polycarboxylic acid component and the polyhydric alcohol component (optionally together with monofunctional components such as monocarboxylic acids, other monohydric alcohols, etc) to yield an acidic polyester; followed by reaction of the polyester with the appropriate long chain alcohol. In the following description the term "starting mixtures" is intended to refer not only to a mixture of the three basic components actually to be polycondensed but also to the theoretical mixture from which the polyester is eventually derived.
As is well known, the nature of a polyester, e.g. its average molecular weight, degree of cross-linking and acid number, will depend upon the nature of the various polyfunctional components, i.e. their degree of functionality, and the ratios between the various components of the starting mixture. The polyesters of the invention are derived from an appropriate starting mixture containing from 5 to 60% percent by weight of long chain alcohol, preferably 10 to 60% by weight thereof, more preferably 20 to 40% by weight thereof and, especially, 22 to 32% by weight thereof. The other components of the starting mixture for the resin are suitably of such a nature and in such amounts that the final polyester has a molecular weight of UP to 20,000, preferably up to 10,000 and more preferably from 400 to 5,000, (especially 500 to 3,000), and an acid number of up to 300 mgKOH/g, more preferably from 0 to 150 mgKOH/g, preferably 4 to 80 mgKOH/g.
The polyesters of the invention are preferably branched rather than linear materials and, thus, at least one of the polyfunctional components should be tri-functional or higher, tri-functionality generally affording sufficient branching. Suitable tri-functional carboxylic acids for use in the preparation of the polyesters include pyromellitic dianhydride and trimellitic anhydride. Suitable polyhydric alcohols include trimethylolpropane, pentaerythritol and glycerol. The polyester will also generally be derived from one or more difunctional components and suitable dicarboxylic acids and dihydric alcohols include isophthalic acid, terep
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Acquah Samuel A.
Coates Brothers PLC
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